1. Field of the Invention
The present invention relates to the field of failure analysis in semiconductor processes, and more particularly, to electron microscopy sample preparation without using a polishing tool, so as to reduce sample preparation costs and time.
2. Description of the Prior Art
As IC technology progresses, electron microscopy is used extensively in failure analysis, especially the transmission electron microscope (TEM). According to the signal obtained from the interaction of particles and electrons, the information to be analyzed by the TEM can be divided into three parts: 1. The displayed image gathered by the transmitted electron or the elastic scattering electron, 2. The electron diffusion pattern (DP) formed for researching tiny tissues and crystal structures, and 3. The chemical composition analysis obtained by using the energy dispersive spectrometer (EDS) or the electron energy loss spectroscope (EELS). With the improvement of instruments, the analytical electron microscope and the high resolution electron microscope can be combined together to display images. With this combination, the nano beam diffraction (NBD) and the convergent beam diffraction (CBD) can be done. It has various abilities to satisfy analytical demands in various ranges.
The TEM instrument system mainly comprises: 1. An electron gun that is one of three types a tungsten filaments electron gun, a LaB6 electron gun, and a field emission electron gun (similar to a scanning electron microscope (SEM)), 2. An electromagnetic lens system that includes a condenser lens, an objective lens, an intermediate lens, and a projective lens, 3. A sample chamber having a sample holder of that is either a side entry type or a top entry type, and 4. An image observation and record system comprising a ZnS/CdS coating fluorescence screen or a photonegative one.
The observation mode of the TEM has two types: a planar observation mode and a cross-section observation mode. In the planar observation mode, electron beams are emitted toward a chip surface vertically to make the right side observation, which is usually for researching the device layout, the materials, or the size measurement. In the cross-section observation mode, a vertical structure of the chip is sideling observed, and it is usually for measuring each layers thickness, researching the material stacked frame, and observing the interface structure. The sample preparation relates to the observation mode. There are two methods of cutting and trimming the sample when observing a routine procedure. The planar observation mode utilizes a chemical solution etching process and the cross-section observation mode utilizes an ion miller to cut and trim the sample. However, the planar observation mode can utilize the ion miller and the cross-section observation mode can utilize a focus ion beam (FIB) to cut and trim the sample for a more precise observation. The FIB allows a lateral orientation on the sample so that the cross-section can be prepared in a selected area, at least within certain boundaries, of the portion of the sample to be analyzed.
The conventional transmission electron microscopy has several limitations including: 1. The thickness of the sample has to be below 3 millimeters (mm), 2. The most ideal observation thickness of the sample is about 500xcx9c1000 angstroms (xc3x85) due to the limitation of the transmission electron beam, 3. The dimension of the observation region is usually below 100 mm due to the difficulty of sample preparation, and 4. In some situations, such as the chip sealing, the cross-section analysis of the single bit failure, or the cross-section analysis of single contact hole, the sample preparation is very difficult, thereby reducing the usefulness of the sample preparation.
In addition, when utilizing a conventional sample polisher such as a Sagitta""s NEXT-1 automatic polisher to prepare the sample, a particular tool manufactured by the polisher factory has to be used in the sample preparation. The particular tool cannot be recycled and has to be molded by itself so as to increase costs of the sample preparation, and more analysis time is needed when using the particular tool to prepare the sample.
It is therefore a primary objective of the claimed invention to provide a novel electron microscope sample preparation without the particular tool to allow relatively fast sample preparation and cost reductions.
According to the claimed invention, a TEM sample preparation is disclosed. A sample polisher including a holder and a chip segment to be tested having a first polishing end, a second polishing end, and a pre-selected testing point between the first polishing end and second polishing end are provided. The chip segment is attached to the holder of the sample polisher, and the first polishing end of the chip segment is polished by using the sample polisher to generate a first polished cross section. The chip segment has a first predetermined distance between the first cross section and the testing point. The chip segment is detached from the holder. A carrier segment is attached to the first cross section of the chip segment. The conjoined carrier segment and the chip segment are attached to a pad segment so as to form a stacked structure. The stacked structure is attached to the holder, and the second polishing end of the chip segment is polished to generate a second polished cross section by using the sample polisher. The chip segment has a second predetermined distance between the second polished cross section and the testing point.
The claimed invention prepares the sample without utilizing the conventional particular tool so as to allow relatively fast sample preparation and cost reduction simultaneously.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.